The invention relates generally to a booster valve assembly for a bi-directional braking system, and specifically to a booster valve assembly where both forward and rearward braking are facilitated by a single booster used for both directions of travel.
Typically, agricultural vehicles require two braking circuits along with master cylinders that work independently of each other. The independent operation of each brake circuit allows for brake steering of the vehicle. Each circuit includes a separate brake pedal corresponding to a left circuit and a right circuit of the motor vehicle. The brake steering allows for tight turning circles of the agricultural vehicle. In such braking systems, the pressure is balanced by a compensating valve that joins two master cylinders along with the corresponding pressure chambers. The coupling of the two master cylinders allows for braking of both circuits.
Many agricultural vehicles are designed for bi-directional operation meaning that an operator of the vehicle can sit either facing forward or facing rearward while operating the vehicle. In such vehicles, separate forward and rear brake pedals are provided for forward and rearward braking. The master cylinder for rearward braking need to engage the same braking circuit as the forward direction brake pedals. Typically, this requires a braking comprising complicated hydraulic circuits and combinations of valves. As appreciated, the use of valving and other complicated fluid pressure routing increases costs along with the complexity of the machine.
Accordingly, it is desirable to design a hydraulic brake booster valve capable of directly operating the vehicle brakes both directly and remotely.
An embodiment of this invention is a hydraulic booster valve including a plunger split into two parts to allow both direct and remote operation.
An embodiment of this invention includes a housing defining an internal bore. A booster piston disposed within the internal bore moves between open and closed positions to regulate fluid pressure between an inlet and outlet. The booster piston is actuated by a plunger disposed within a plunger bore within the booster piston. Movement of the booster piston within the internal bore covers and uncovers an inlet port. The inlet port receives pressure from the pressure inlet and directs that pressure against the booster piston to bias the booster piston for the actuation of the brake assembly.
The booster piston is actuated for movement along and within the internal bore by movement of the plunger assembly. The plunger assembly includes a first and second plunger that is movable within the internal plunger bore. The first plunger is attached to a push rod actuated by a forward brake pedal. The second plunger is movable relative to the first plunger and includes an internal passageway aligning with an inlet port defined by the booster piston. A second inlet port communicating with a master cylinder actuated by a rear brake pedal provides fluid pressure to an annular passage defined in the second plunger. The annular passageway provides fluid communication between the second inlet port and an area disposed between the first and second plunger.
Actuation of the booster piston by a forward brake pedal is accomplished by pushing the push rod which in turn moves the first plunger against the second plunger towards alignment of the internal passageway defined by the second plunger with an inlet port. As the inlet port aligns with the internal passageways of the second plunger fluid pressure is allowed to communicate with a plunger bore within the booster piston to force the booster piston to allow pressure to flow from the inlet.
When an operator is actuating brake pedals from the rearward position, the first plunger remains at its initial location within the plunger bore. Fluid pressure allowed into the second inlet and through the annular passageway between the area between the first and second plunger forces the second plunger towards alignment with the inlet port. The first plunger is forced in an opposite direction and held from exiting the plunger bore by a clip. The clip prevents movement of the first plunger beyond a rest position.
The valve includes a direct twin compact booster with a plunger split into two parts. The first plunger sticks directly to the forward pedals by the push rod. The first plunger is retained by a clip within the plunger bore. The second plunger is connected hydraulically to the rearward pedals. Both the first and second plungers slide within the plunger bore. The hydraulic fluid used to operate the second plunger is sealed by various seals disposed on the second plunger. Because both plungers are disposed within the plunger bore and include a uniform diameter along its length, both plungers operate the booster with the same booster ratio. In other words, the forward and rearward brakes will operate the brakes such that the common proportions of pedal movement will result in the same proportion of braking force.
Accordingly, a single hydraulic booster valve and master cylinder are actuatable by both forward and rear pedals simplifying operation and construction of the braking system.